This invention relates to nitrogen doping of III-V photocathode material to increase the photocathode quantum efficiency, and more particularly to nitrogen doping of III-V photocathode material for improved quantum efficiency.
The development of III-V photocathodes has undergone sufficient study for their method of operation to be fairly well understood. In Cs.sub.2 O-activated III-V photocathodes, a quantum efficiency of 7.5% has been achieved at 1.06 microns. L. W. James, G. A. Antypas, R. L. Moon, J. Edgecumbe and R. L. Bell, Appl. Phys. Letters 22, 270 (1973). The operation (photoemission process) could be broken down into its component parts of electron-hole pair generation and electron transport through each section and across each barrier in the photocathode. Each component part could be treated and optimized separately. The goal would be to combine all of the optimized parts into a photocathode with the highest possible quantum efficiency. However, the present invention treats only one part, namely the electron-hole pair generation.
Although the present invention does treat only one part, brief reference will be made to other parts of the photoemission process in order to place the invention in proper perspective. To facilitate that, reference will be made to exemplary III-V semiconductor materials for a photocathode sensitive to 1.06 micron, although it will be apparent that other materials, particularly materials selected for other wavelengths, can also employ the present invention to advantage. Reference will also be made to particular activation material, but other material may be used for the activation layer.